It was the first time the US has scrambled aircraft in response to Syrian efforts to blunt Kurdish advances.

The Kurdish YPG militia holds a large area in northern Syria. The Kurds declared the region autonomous following the beginning of the foreign intervention in Syria in 2011.

In addition to airstrikes, the Syrian government has bombarded Kurdish districts of Hassakeh with artillery.

In May, US commandos were photographed with Kurdish fighters.

“US advisors have been assisting the Kurds and other groups fighting the Islamic State and Syrian President Bashar al-Assad’s regime in Syria, but this is the first time US troops have been documented taking part in the fighting on the ground against the Islamic State in an offensive manner. American warplanes have been bombing IS positions in support of the SDF and other Syrian groups for months,” Vice News reported on May 27.

Turkey accused the United States of “unacceptable” behavior after the photographs showed the commandos wearing Kurdish insignia.

The Pentagon ordered the Green Berets to remove the YPG patches.

Ankara considers the YPG terrorists. It says the group is aligned with the Syrian branch of the Kurdistan Workers’ Party which has fought an insurgency with Turkey for over three decades.

In October, Obama ordered the deployment of 50 commandos. A senior Pentagon official said the forces would be there in “a strictly advise and assist mission” but would “not be going out and doing joint operations” with the Kurds.

In April, he added and additional 250 commandos. The following month, Gen. Joseph Votel, head of the U.S. Central Command, visited Kobani to meet with local Arab and Syrian Democratic Forces leaders. The SDF is a creation of the United States.

The photos taken in May show the US Special Operations Forces patrolling the village of Fatisah north of the Islamic State held city of Raqqa.

Earlier this month, the BBC released photos showing British commandos equipped with sniper rifles, anti-tank missiles and artillery on Syrian territory near the border with Jordan. The troops were reportedly engaged in combat with the Islamic State.

“We are receiving special forces training from our British and American partners. We’re also getting weapons and equipment from the Pentagon as well as complete air support,” a New Syrian Army spokesman told the BBC.

The New Syrian Army is a CIA created mercenary group. It was deployed at al-Tanf in southeastern Syria, near the Jordanian border, in late 2015. It is associated with another manufactured rebel group, Ahmad al-Abdo Martyrs Brigades and Battalions.